Hi all! Here is some basic suggestions and guidelines for the raid battles based on the limited knowledge I have gained since it opened. Feel free to post corrections, ideas, or questions in the comments below!

General Rules and Observations:
In order to participate in a raid battle, you need to: Complete the Scenario Stages, Enter a Dimensional Rift using Dimensional Crystals, Attack the World Boss, Rift of Worlds Opens!

A raid battle involves 3 different Summoners each with teams of 6 battling one boss with 3 different heads. The boss will have one HP bar, but 3 different attack bars: one for each head. Harmful effects placed on the boss will apply to all 3 heads.

Boss is immune to stuns, freezes, provoke, sleep, DOTS.

Find a team of 3 people that you intend to stick with. EVEN IF YOU CANT BEAT LEVEL 1 RIGHT NOW, WORK TOGETHER TO CREATE A TEAM WITH SYNERGY.You are much more likely to be successful when battling with teammates that you can plan and build up a specific team with synergy.

Removes all beneficial effects - heals based on the number of beneficial effects removed

Debuffs: Stun

Permanently increases Boss's attack power

Total Annihilation:

Attacks automatically whenever the boss loses 25% of the HP

AoE

Removes all harmful effects on the boss

Boss's stats will substantially increase when this skill is activated

Crush of Doom and Breath of Doom with gain an additional hit whenever Total Annihilation is activated.

Carnage

When the boss eliminates an entire team of Monsters, the boss's SPD will increase and will start attacking the nearby team of enemies.

Destroyer's Revenge (Passive)

The damage of the next attack will increase in proportion to the number of the enemy's turn. The damage will reset after the attack.

Ruler of Chaos (Passive)

The 3 heads of the boss will share the attack gauge at the start of the battle using its chaotic strength. Also, the boss will mitigate HP proportionate damage it receives by sharing a single HP among the 3 heads.

Personal Team Composition:Frontline and Backline:
The first thing to note is: there is a FRONTLINE and a BACKLINE. Each can contain a maximum of 4 of your monsters.
Your personal team will have a FRONTLINE and a BACKLINE. The backline will take a smaller percentage of damage based on the damage your frontline takes.Frontline monsters should be DEFENSE MONSTERS. Not just tanky monsters with high HP. The higher the defense, the less damage your backline will take - and the less damage your frontline will take from Crush of Doom.

Overall Team Composition:Debuffs:
Debuffs will apply to all 3 heads. At minimum, you only need 1 reliable monster for each debuff.PREFERABLE: Glancing Hit, HP disturb, ATK, Defense, SPDBuffs:Buffs will only apply to your personal team. You will need at least one of each buffer on every personal team.
The boss has many debuffs. You need to have at least one harmful effect remover per team.PREFERABLE: Immunity, Harmful Effect Remove
HELPFUL: ATK, DEF, SPDLeader Skills:
Leader skills are shared over all allies.
Same leader skills do not stack [i.e. HP% and HP% leader skills will not stack, however HP% and HP% of Fire Monsters WILL stack]The LEADER SKILLS that are very important to have are: DEF% (or HP%), SPD, Resistance
[Notes: Okay-ish substitute for SPD: ATK]
[This is not a dungeon. Leader skills that apply only in dungeons will not apply here.]

Look at all those (nat) Five stars!
I don't have any (nat) five stars so i can't survive at all! lol only have 1 six star

Click to expand...

Heeh yeah I include the nat 5*s in this guide because a fair amount of people seriously looking to progress in raid battles have at least 1 nat 5*. This guide is more for serious progression in raids than starting out in them, for starting out you just want to use your best monsters while loosely following the desired elements of a team.
My current team is: [[ Velajuel, Talc, Driller ]] [[ Jamire(lead), Ethna, Belladeon ]] -- which is only half recommended monsters, but works for Level 3.